1. Field of the Invention
The present invention relates to a method for the preparation of new compounds with built-in isocyanuric groups as well as with the compounds obtained by this method.
2. Description of the Prior Art
The preparation of masked isocyanates, also called isocyanate yielders, is known and is described in Houben-Weyl, Methoden der organischen Chemie, XIV/2 pp. 61-70. It is known to use as blocking agents, tertiary alcholos, phenols, acetoacetic ester, malonic acid ester, acetyl acetonate, phthalimide, imidazole, hydrogen chloride, hydrogen cyanide and .epsilon.-caprolactam.
These masked isocyanates possess the property of reacting, at higher temperatures, as isocyanates. The splitting of the masking group is easier, the more acidic the hydrogen atom of the masking group. Such blocked isocyanates are described in the DT-OS 21 66 423. Terminally blocked isocyanates, which also contain in addition uretidione groups, are described in DT-OS 25 02 934.
Surprisingly, the literature does not contain any reference to isocyanuric groups containing terminally blocked isocyanate groups with aliphatic polyisocyanates. Blocked aromatic isocyanurates are reported for the preparation of heat resistant grinding resistant urethane-enamel, especially for electric wire insulators, in JA-AS No. 73-30453, filed on Dec. 24, 1969. The preparation of aliphatic polyisocyanate-containing thus blocked isocyanuric groups is on the other hand, unknown until now.